Rare blindcat found in US, could prove water-filled caves connect Texas and Mexico

The extremely rare cave-dwelling albino fish with no eyes, the Mexican blindcat, has previously only been known to exist in Mexico.

In 2015 in a deep limestone cave at Amistad National Recreation Area in Texas, caver and National Park Service resource manager, Jack Johnson, spied some curious languid fish; slow-moving, light pink and no eyes. Rumors of such fish in the area had been floating around for half a century; without confirmation they remained a myth. But last month when Johnson returned with biologist Peter Sprouse and a team searching for the fish again, they found two of them. They have since been identified as the endangered Mexican blindcat (Prietella phreatophila).

The small Mexican blindcat is known to live only in areas supported by the Edwards-Trinity Aquifer that underlies the Rio Grande basin in Texas and the northern Mexican state of Coahuila. The new blindcat finding lends additional weight to a theory that water-filled caves below the Rio Grande may connect the Texas and Mexico portions of the aquifer, says The University of Texas at Austin.

Dean Hendrickson, curator of ichthyology at The University of Texas at Austin, who identified the fish, says that the Texas fish appear to be the same as their brethren from south of the border.

"Since the 1960s there have been rumors of sightings of blind, white catfishes in that area, but this is the first confirmation," Hendrickson said. "I've seen more of these things than anybody, and these specimens look just like the ones from Mexico."

They are extraordinary creatures. They live exclusively in groundwater, and their pale peony-pink blush is due to the fact that their translucent skin allows the color of blood to shine through. They have no eyes; who needs eyes when you live in deep dark caves?

"Cave-dwelling animals are fascinating in that they have lost many of the characteristics we are familiar with in surface animals, such as eyes, pigmentation for camouflage, and speed," Sprouse said. "They have found an ecological niche where none of those things are needed, and in there they have evolved extra-sensory abilities to succeed in total darkness."

The first Mexican blindcat to be described was discovered in 1954 in wells and springs near Melchor Múzquiz in Coahuila. The Mexican government listed it as an endangered species; the U.S. Fish and Wildlife Service listed it as a foreign endangered species.

"Aquifer systems like the one that supports this rare fish are also the lifeblood of human populations and face threats from contamination and over-pumping of groundwater," Johnson said. "The health of rare and endangered species like this fish at Amistad can help indicate the overall health of the aquifer and water resources upon which many people depend."

The fish have been relocated to the San Antonio Zoo, where they will live their cave-fish lives in a special facility created for cave and aquifer species at the zoo’s Department of Conservation and Research.

(Which of course brings about questions of captivity versus conservation – but I digress.)

"The San Antonio Zoo has a series of labs specially designed to keep subterranean wildlife safe and healthy," says Danté Fenolio, vice president of conservation and research at the San Antonio Zoo. "The fact that the zoo can participate now and house these very special catfish demonstrates the zoo's commitment to the conservation of creatures that live in groundwater."

The discovery raises the number of blind catfish species in the U.S. to three, all which dwell only in Texas. The other two are the toothless blindcat (Trogloglanis pattersoni) and the widemouth blindcat (Satan eurystomus), which live in part of the Edwards Aquifer complex below the city of San Antonio. Which is really pretty amazing; as we humans go about doing our human things, there can be incredible nature taking place right below our feet, nature as fascinating as slow-moving translucent pink fish with no eyes.